During shipping, processing, storage, or disposal bulk materials may concentrate in a particular area or site. Bulk materials concentrated into piles must be covered to minimize or prevent blowing dust or debris; water damage; odor; prevent fires; or movement or erosion of material; or prevent vectors such as birds, flies, and/or other insects from feeding thereon. Typically bulk materials are covered by spreading a synthetic material such as a tarp or foam over exposed portions of the pile. For example, in power plants, piles of coal may be covered by spreading an elastomeric geomembrane thereon; the thickness and construction of the membrane depends on the length of time the pile is to remain covered and the expected climatic conditions. One problem associated with the use of membrane covers is the high labor cost and worker safety concerns associated with physical placement of such membranes.
Regulatory agencies require that landfills must be covered at the end of every workday in order to minimize the potential for odors, ground water contamination, fires, blowing litter, disease vectors, and vermin infestation. Many current regulations require daily coverage of exposed waste with a daily cover including a minimum of six (eight in some locations) inches of soil applied to the landfill workface. Due to the non-homogeneous layout of most landfills, such a layer of soil may actually reach from 12 to 15 inches in height in certain areas in order to ensure that the six-inch minimum cover exists throughout. It is estimated that the use of a six-inch soil daily cover will use up 25% of the total landfill space. The use of soil daily cover also requires a significant amount of labor and heavy-duty equipment to transport and compact the soil. Because waste storage capacity is a landfill's most precious commodity, the traditional soil method of covering the waste has become less and less popular in recent years. In response to the recent demands for more efficient usage of landfill space, alternative daily cover, or ADC, systems have been attracting more and more attention during the past decade. The primary goal of an ADC is to perform all of the functions of a six to eight inch layer of soil without the drawback of consuming large amounts of landfill capacity.
U.S. Pat. No. 4,421,788 to Kramer et al. describes a hardenable plastic foam cover which is formed by spraying over waste materials. Similarly, companies such as 3M Environmental Protection Products of St. Paul, Minn., Chubb Environmental Security of Exton, Pa., and Russmer of Westchester, Pa., all have developed synthetic foams which can be sprayed to function as a daily cover. The foam spray solution is expensive, typically 12 to 15 cents per square foot, substantially more expensive than soil. Also, the safety of these chemical formulations has been questioned and their effect upon ground water quality remains unknown.
Another disadvantage of the daily foam cover substitutes is that they cannot be easily formulated from recycled materials. The increasing sensitivity towards the environment by the general population has greatly increased the demand for recycled products. Federal, state, provincial and municipal environmental officials, who operate or regulate most landfills, have been especially active in encouraging the use of recycled products. Among the advantages of recycling is the fact that the waste material is converted into useful products rather than taking up rapidly vanishing landfill space. Hence, such officials are making great efforts to integrate recycled materials into operations under their control, including landfill operations.
Another alternative to using soil as a daily cover is disclosed in U.S. Pat. No. 4,909,667 to DeMello and U.S. Pat. No. 4,927,317 to Acosta, DeMello and Acosta disclose a geotextile or sheet-like member, such as canvas and the like, which is laid over the working face of a landfill at the end of the operating day. A key disadvantage of geotextile covers is their expense which may be as high as $2.25 per square yard. In addition, geotextiles are subject to mechanical damage, such as tears, punctures, requiring replacement or repair. Moreover, these covers are difficult to apply in inclement weather.
A daily cover system and method for production of a cover system has been disclosed in U.S. Pat. No. 5,161,915 issued Nov. 10, 1992, and U.S. Pat. No. 5,525,009 issued Jun. 11, 1996 to Hansen. The cover system primarily uses cement kiln dust or Portland cement and fly ash, or Portland cement and crushed stone dust as a binder. Many landfill operations have experienced problems with this type of cover with adherence to plastics and glass in the landfilled waste.
U.S. Pat. No. 5,516,830 to Nachtman, et al discloses a composition which composes gypsum, water-soluble cellulosic polymer and fiber. In the of U.S. Pat. No. 6,096,373 to Nachtman et al, it discloses a landfill cover composition and method, which uses setting material, water soluble cellulosic polymer, fibrous material, a foam producing agent and water for forming a foamed outdoor protective cover layer. The mixing system contains a foam generator, which makes the mixing process and equipment very complicated. Actually, most of the air bubbles in the foamed slurry will break during the spray, especially.
United States Gypsum Company has been marketing an industrial grade gypsum based product called Airtrol Plaster®, which is mixed with cellulose fiber mulch and water to form a slurry and is sprayed for a landfill cover or erosion control. Recently, in U.S. Pat. No. 6,435,770 to Shi discloses a cover system which uses processed dry walls as binder. The gypsum based cover systems also have problems with adherence to plastics and glass in the landfilled waste.
Latex paint now accounts for over 80% of consumer paint. A survey in by the Wisconsin Department of Natural Resources contracted with Cascadia Consulting Group in 2002 indicated that the quantity of latex paint in landfilled wastes could be up to 0.3%, with an average of 0.1%. Latex paint or paint sludge may be dried prior to disposal in a landfill. Paint recycling programs have been established in some jurisdictions to recover the paint for recycling. However waste latex paint or paint sludge from recycling operations is still a significant post-consumer product that needs management.